When I yoyo I sometimes feel like the string is going to break any second. But it doesn’t. When it does though, I want to get yoyo string and not wait for delivery. Is there any kind of string you can get in a hardware store or somewhere not online. If not say so. If so, where and what kind and what’s it called?

You may be able to find some at a hobby shop of the sort? If you generally say where you live, someone may be able to help.
You can also make your own string. Just look up on YouTube “how to make yoyo string.”

If you have more questions feel free to ask, but it is also more important to research things on your own.